The invention relates to an optical measuring head for an automatic laboratory chemical or biochemical reaction analyser designed to determine the dosing of components contained in samples after mixing with reagents in cups of a reaction analysis plate, said measuring head comprising:
a first calorimetric analysis detector controlled by a light source associated to an optic fibre for transmission of the light beam to one of the sides of the reaction analysis plate, coinciding with the optic axis of a predetermined cup, which cup is made of transparent material,
means for focussing the light beam when the latter passes through the reaction mixture in said cup,
a photodetector device arranged on the opposite side of the analysis plate to collect the light beam emerging from the cup after this beam has been subjected to an attenuation,
and an electronic processing circuit for processing the signal delivered by the photodetector device to determine the light spectrum or the optical density of the reaction mixture.
To perform measurement of the optical density of a solid, liquid or gas medium, it is necessary to have a reference light source. This light source operates in conjunction with an optical focussing, collimation or filtering system to generate the incident beam
The whole of the measurement chain is mobile and the analysis plate samples are fixed. Vibrations of the filament lamps can however give rise to measurement errors and reduce the lifetime of the lamps.
A first object of the invention is to achieve an improved optical measuring head for a sample analyser by high precision colorimetry.
A second object of the invention is to achieve a multiple optical measuring head suitable for an automatic analyser integrating at least two measuring systems for different applications and enabling the same sample and reagent storage equipment, the same sampling equipment and the same analysis plate to be kept.
The optical measuring head according to the invention is characterized in that:
the light source and the reaction analysis plate are fixed,
the measuring head comprises a U-shaped mobile support framing the parallel opposite sides of the reaction analysis plate and a drive mechanism of said mobile support to bring the first colorimetric analysis detector to face a predetermined cup,
the optic fibre has one end secured to the fixed light source and an opposite end arranged in a first housing of the mobile support.
The light source and the analysis plate are isolated from the measuring head, and the advantage of the system lies in the fact that the light source and the sample to be analysed are protected from mechanical vibrations. The optic fibre arranged between the fixed light source and the bottom part of the mobile support is alone subjected to torsional and flectional deformation movements during positioning of the measuring head. To prevent premature wear of the optic fibre due to the mechanical frictions caused by deformation, optic fibres provided with an external protective film made of highly resistant material should advantageously be used.
According to a preferred embodiment, the first housing of the mobile support contains an optical collimator to deliver a parallel light beam and a reference photoelectric detector connected to the electronic circuit to compensate the light flux variations when deformation of the optic fibre occurs. A second housing is located opposite the first housing and contains an optical focussing system optically linked with the photo-detector device.
According to one feature of the invention, the optical focussing system of the photo-detector device is connected to a diffraction network for static wavelength selection.
According to a development of the invention, the measuring head is equipped with a second photometric analysis detector arranged on the mobile support to perform an opacimetry measurement. The second photometric analysis detector comprises at least one light-emitting diode for emission of a monochromatic light, operating in conjunction with a receiver photodiode on the opposite side of the mobile support.
It is thus possible to integrate two different reading systems in the measuring head of an analyser, enabling analyses to be performed on the one hand in biochemistry and immunology and on the other hand for hemostatic reactions, using the same sample and reagent storage equipment, the same sampling equipment, and the same analysis plate.
In the analyser using the measuring head according to the invention, the bottom face of the analysis plate is confined in an enclosure kept at a preset temperature by a thermostatic control. The enclosure is advantageously provided with a deformable flexible wall allowing the mobile support to move under the analysis plate.
According to another feature of the invention, the bottom face of the analysis plate is confined in an enclosure kept at a preset temperature by a thermostatic control. The enclosure is advantageously provided with a deformable flexible wall allowing the mobile support to move under the analysis plate.